System and method for multiple backplane time synchronization

ABSTRACT

A system and method for synchronizing multiple backplanes within an information handling system are disclosed. An information handling system includes a first controller that may be operable to generate a time command at a predetermined time interval. A backplane including a second controller is communicatively coupled to the first controller. The second controller may be operable to receive the time command from the first controller and calculate a skew for the time command based at least on a location of the backplane. The second controller may further be operable to adjust a time domain of the backplane based on the calculated skew for the time command to synchronize the backplane.

TECHNICAL FIELD

The present disclosure relates in general to information handlingsystems, and more particularly to a system and method for multiplebackplane time synchronization.

BACKGROUND

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to users is information handling systems. Aninformation handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may also vary regarding what information is handled,how the information is handled, how much information is processed,stored, or communicated, and how quickly and efficiently the informationmay be processed, stored, or communicated. The variations in informationhandling systems allow for information handling systems to be general orconfigured for a specific user or specific use such as financialtransaction processing, airline reservations, enterprise data storage,or global communications. In addition, information handling systems mayinclude a variety of hardware and software components that may beconfigured to process, store, and communicate information and mayinclude one or more computer systems, data storage systems, andnetworking systems.

As information handling systems become more complex due to increasingoperating demands, there is a need for increased storage density and adesire for modularity that results in the use of backplaneconfigurations. Current information handling systems may supportmultiple types of storage controllers (e.g., host bus adaptor (HBA),chipset serial attached SCSI (SAS), chipset peripheral componentinterconnect (PCI), etc.) and various storage technologies (e.g.,mechanical motor, SAS, PCIs, solid state drive (SSD), etc.) attached tomultiple modular backplanes. Generally, these backplanes are allindependently managed by the onboard storage enclosure processor (SEP),such that the backplanes are in disparate time domains and are notsynchronized.

SUMMARY

In accordance with the present disclosure, the disadvantages andproblems associated with synchronizing multiple back planes have beensubstantially reduced or eliminated. In a particular embodiment, aninformation handling system includes a first controller that may beoperable to generate a time command at a predetermined time interval. Abackplane including a second controller may be communicatively coupledto the first controller. The second controller may be operable toreceive the time command from the first controller and calculate a skewfor the time command based at least on a location of the backplane. Thesecond controller may further be operable to adjust a time domain of thebackplane based on the calculated skew for the time command tosynchronize the backplane.

In accordance with a another embodiment of the present disclosure, acontroller configured to provide time synchronization in a backplaneincludes a processor communicatively coupled to a memory and processinginstructions encoded in the memory. The processing instructions, whenexecuted by the processor, may be operable to perform operationsincluding receiving a time command and calculating a skew for the timecommand based at least on a location of a backplane associated with thecontroller. The processing instructions further may be operable toperform operations including adjusting a time domain of the backplanebased on the calculated skew for the time command to synchronize thebackplane.

In accordance with a further embodiment of the present disclosure, amethod for providing time synchronization in a backplane includesreceiving a time command from a first controller at a second controllerassociated with a backplane and calculating a skew for the time commandbased at least on a location of the backplane. A time domain of thebackplane may be adjusted based on the calculated skew for the timecommand to synchronize the backplane.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIGS. 1A-1B illustrate block diagrams of example embodiments of aninformation handling system configured for time synchronization acrossmultiple backplanes in accordance with the teachings of the presentdisclosure; and

FIG. 2 illustrates a flow chart of an example method for providing atime synchronization across multiple backplanes in accordance with theteachings of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure and their advantages are bestunderstood by reference to FIGS. 1 and 2, where like numbers are used toindicate like and corresponding parts.

For the purposes of this disclosure, an information handling system mayinclude any instrumentality or aggregate of instrumentalities operableto compute, classify, process, transmit, receive, retrieve, originate,switch, store, display, manifest, detect, record, reproduce, handle, orutilize any form of information, intelligence, or data for business,scientific, control, entertainment, or other purposes. For example, aninformation handling system may be a personal computer, a PDA, aconsumer electronic device, a network storage device, or any othersuitable device and may vary in size, shape, performance, functionality,and price. The information handling system may include memory, one ormore processing resources such as a central processing unit (CPU) orhardware or software control logic. Additional components of theinformation handling system may include one or more storage devices, oneor more communications ports for communicating with external devices aswell as various input and output (I/O) devices, such as a keyboard, amouse, and a video display. The information handling system may alsoinclude one or more buses operable to transmit communication between thevarious hardware components.

FIG. 1A illustrates a block diagram of example information handlingsystem 100 including host 101 having controller 110 configured toprovide time synchronization across multiple backplanes 116 inaccordance with the teachings of the present disclosure. Informationhandling system 100 may be a modular system that includes multiple bayswhere each bay includes one or more devices (e.g., blades) associatedwith at least one backplane controller. In some embodiments, informationhandling system 100 may include host 101 communicatively coupled tobackplanes 116.

Host 101 may generally be operable to receive data from and/orcommunicate data to one or more other information handling systems via anetwork (not expressly shown). In certain embodiments, host 101 may be aserver. In another embodiment, host 101 may be a personal computer(e.g., a desktop computer or a portable computer). As depicted in FIG.1, host 101 may include controller 110 communicatively coupled to (MUX)112 and network interface 104. Host 101 may also include a memory and aprocess (not expressly shown) for storing and executing programinstructions.

Controller 110 may include any element, device, and/or programmingoperable to communicatively couple with processor 102 and facilitateoperation of information handling system 100. For example, controller110 may be a baseboard management controller (BMC) and/or a remoteaccess controller (RAC) (e.g., a Dell Remote Access Controller (DRAC) oran Integrated Dell Remote Access Controller (iDRAC)) configured togenerate a time command and send the time command to backplanecontrollers 114 of backplanes 116, which use the time command tointernally skew the time domain of backplanes 116 based on the location(e.g., bay number) of backplanes 116. Controller 110 may includeprocessor 102 and memory 108 communicatively coupled to the processor.

Processor 102 may comprise any system, device, or apparatus operable tointerpret and/or execute program instructions and/or process data, andmay include, without limitation, a microprocessor, microcontroller,digital signal processor (DSP), application specific integrated circuit(ASIC), or any other digital or analog circuitry configured to interpretand/or execute program instructions and/or process data. In someembodiments, processor 102 may interpret and/or execute programinstructions and/or process data stored in memory 108 and/or anothercomponent of information handling system 100 and may output results,graphical user interfaces (GUIs), websites, and the like via display 106or over network interface 104.

Memory 108 may be communicatively coupled to processor 102 and maycomprise any system, device, or apparatus operable to retain programinstructions or data for a period of time. Memory 108 may compriserandom access memory (RAM), electrically erasable programmable read-onlymemory (EEPROM), a PCMCIA card, flash memory, or any suitable selectionand/or array of volatile or non-volatile memory that retains data afterpower to information handling system 100 is turned off.

Network interface 104 may be any suitable system, apparatus, or deviceoperable to serve as an interface between information handling system100 and a network (not expressly shown). Network interface 104 mayenable information handling system 100 to communicate over a networkusing any suitable transmission protocol and/or standard, includingwithout limitation all transmission protocols and/or standards known inthe art. Although network interface 104 is illustrated as being separatefrom controller 110 in FIGS. 1A and 1B, network interface 104 may beintegral to controller 110.

Multiplexer (MUX) 112 may be a general purpose Input/Output (I/O) basedMUX and may be configured to communicatively couple backplanecontrollers 114 to controller 110. MUX 112 may further be configured toreceive a MUX control command from controller 110 in order to select oneof backplane controllers 114 for receiving the time command. AlthoughMUX 112 is illustrated as being separate from controller 110 in FIGS. 1Aand 1B, MUX 112 may be integral to controller 110.

Display 106 may be communicatively coupled to host 101 and comprise anydisplay device suitable for creating graphic images and/or alphanumericcharacters recognizable to a user, and may include, for example, aliquid crystal display (LCD) or a cathode ray tube (CRT).

Backplanes 116 may be communicatively coupled to controller 110 and maybe any one of a SEP backplane, a serial attached SCSI (SAS) backplane, aSAS extender backplane, and/or any other suitable backplaneconfigurations. In the illustrated embodiment, each of backplanes 116may include backplane controller 114 and visual indicator 120.Additionally, any number of devices and/or storage resources, such asfor example, hard disk drives, solid state drives, just a bunch of disks(JBOD), etc may be coupled to backplanes 116.

At startup, the devices associated with each backplane 116 may haveunique startup sequences that affect the initiation of the clocks andtimers in the devices. Therefore, each backplane 116 may have a uniquetime domain that operates asynchronously to the time domains of theother backplanes. In addition, backplanes 116 may enter a sleep mode forpower savings and/or devices may be added (e.g., hot plugged) duringoperation of information handling system 100. These devices may alsohave asynchronous time domains. Given that data is constantly beingupdated on the devices, it may be preferable to ensure that two or moreof backplanes 116 across information handling system 100 aresynchronized when information is exchanged between the devices indifferent backplanes 116. Furthermore, backplanes 116 may includedevices that are located in different bays but that are grouped intological units such that the group of devices acts as a contiguousstorage unit. Thus, providing a single time domain for the group ofdevices may be preferable in order to maintain data accuracy between thedevices associated with different backplanes 116.

Backplane controllers 114 may be configured to receive the time commandsent from controller 110 and may calculate the skew for associatedbackplanes 116 in order to synchronize backplanes 116 in one timedomain. In some embodiments, backplane controllers 114 may be a storageenclosure processor (SEP) controller or other suitable controllerconfigured to receive a time command and calculate a skew in the timedomain for backplanes 116.

Backplane controllers 114 may include processor 113 and memory 115communicatively coupled to processor 113. Processor 113 may comprise anysystem, device, or apparatus operable to interpret and/or executeprogram instructions and/or process data, and may include, withoutlimitation, a microprocessor, microcontroller, digital signal processor(DSP), application specific integrated circuit (ASIC), or any otherdigital or analog circuitry configured to interpret and/or executeprogram instructions and/or process data stored in the memory. Memory115 may comprise any system, device, or apparatus operable to retainprogram instructions or data for a period of time. For example, memory115 may comprise random access memory (RAM), electrically erasableprogrammable read-only memory (EEPROM), a PCMCIA card, flash memory, orany suitable selection and/or array of volatile or non-volatile memorythat retains data after power to information handling system 100 isturned off.

In some embodiments, each of backplane controllers 114 may receive thetime command from controller 110 at different times. For example,backplane controller 114A associated with Bay 0 may receive a firstbroadcast of the time command and backplane controller 114B associatedwith Bay 1 may receive a second broadcast of the time command, where thesecond broadcast is at later point in time than the first broadcast.Backplane controllers 114, knowing the location (e.g., bay number) ofthe associated backplane 116 with respect to other backplanes 116 ininformation handling system 100, may determine a skew for the receivedtime command in order to synchronize the time domains of backplanes 116.For example, backplane controllers 114 may use the following equation todetermine the skew for associated backplanes 116:Backplane Skew=(Delay of time command)*(Bay Number+1)where the “delay of time command” may account for at least the durationof a time command, the time at which the time command was sent bycontroller 110 and the delay between controller 110 and backplane 116,including the delay through MUX 112 and/or other transmittal delays.

In operation, controller 110 may generate a time command at apredetermined time interval set arbitrarily by processor 102, or a userof information handling system 100 and broadcast the time command to allor some of backplanes 116 via MUX 112. Based at least on the time atwhich controller 110 broadcasted the time command, the delay betweencontroller 110 and backplanes 116, and the location of each backplane116, each backplane controller 114 may skew the time command for anassociated one of backplanes 116 such that the time domains aresubstantially synchronous across all or some of backplanes 116.

For example, referring to FIG. 1A, controller 110 may begin by sending astatus command to each of the bays to determine if the bay is populatedwith a device and that device is active. If the status command indicatesthat a device is present and active in one or more of the bays,controller 110 may generate a time command and send the time command toone of backplanes 116 via MUX 112 at a first time interval. In oneembodiment, the status and time commands may be part of a beacon routinefor use on an I2C bus. If the status command determines that a device isnot present and/or active in one of the bays, controller 110 may enter await state for approximately the duration of one time command. In oneembodiment, the duration of a time command may be calculated based theclock rate of the bus, the number of clocks for a time command, the timefor the select toggle of MUX 112 and the stop setup. For example, theequation to calculate the duration of a time command may be as follows:(Duration of time command)=((Bus clock rate)* (Number of clocks for atime command))+(MUX control toggle time)+(Stop setup)

In some embodiments, the devices associated with backplanes 116 may beorganized into logical groups and controller 110 may broadcast a timecommand to backplanes 116 based on the logical groups. For example,backplanes 116 may be physically located in separate bays but certainones of the devices associated with backplanes 116 may be organized intoone or more logical groups. In one example, the devices associated withbackplanes 116A and 116C may be a first logical group and the devicesassociated with backplanes 116B and 116 n may be a second logical group.In this example, controller 110 may broadcast a first time command forthe first group in order to synchronize the time domains of backplanes116A and 116C associated with the devices in the first group and maybroadcast a second time command for the second group in order tosynchronize the time domains of backplanes 116B and 116 n associatedwith the devices in the second group. The time domain of backplanes 116Aand 116C in the first logical group may be different than the timedomain of backplanes 116B and 116 n in the second logical group.Controller 110 may broadcast the respective time command to each ofbackplanes 116 in the first or second logical groups at a predeterminedinterval. In other embodiments, the devices associated with backplanes116 may not be separated into groups and the time command sent bycontroller 110 may be used to synchronize the time domains of allbackplanes 116.

When the time command is received at backplanes 116, backplanecontrollers 114 may generate an interrupt in order to calculate the skewtime for associated backplane 116. As described above, the skew forbackplanes 116 may be calculated based on the location of the backplane(e.g., the bay number) and the delay of the time command. In oneembodiment, backplane controllers 114 may calculate the delay of thetime command based on the order in which controller 110 sends a timecommand to each of backplane controllers 114. For example, controller110 may broadcast time command at a first time to backplane controller114A and at a second time, which is later than the first time, tobackplane controller 114B. In some embodiments, backplane controllers114 may also determine the delay time between when the time command issent from controller 110 and when the time command is received atbackplanes 116. This delay time may include the delay caused by MUX 112,any setup delays, toggle delays, and/or other delays. Once the delay forthe time command is determined, backplane controllers 114 may calculatethe skew for the time command and may subsequently adjust the timedomain of associated backplanes 116 based on the skewed time command inorder to synchronize backplanes 116 in one time domain.

Referring to FIG. 1B, backplanes 116B and 116C may be arranged in adaisy-chain configuration. In some embodiments, backplane controller114B may be configured to synchronize the primary backplane, e.g.,backplane 116B by determining the delay between the time at whichcontroller 110 sends the time command and when backplane controller 114Breceives the time command, the delay caused by MUX 112, setup delays,toggle delays, any previous bay synchronization delays (e.g., delaysfrom synchronizing backplane 116A), wait state delays, and/or any otherdelays. Once the primary backplane is synchronized, the slave backplane,e.g., backplane 116C may be synchronized by backplane controller 114C.In some embodiments, primary backplane 116B may synchronize slavebackplane 116C by determining the delay between the two backplanes andmay provide the updated time command to slave backplane 116C.Additionally, as described in the example embodiments above, thesynchronization may occur via the I2C bus that may interconnect thecomponents of information handling system 100. For example, backplanecontroller 114B may master the bus and communicate commands to slavedevices such as backplane 116C to complete synchronization ofinformation handling system 100.

FIG. 2 illustrates a flow chart of a method for providing a timesynchronization across multiple backplanes in accordance with certainembodiments of the present disclosure. Generally, controller 110 maybroadcast a time command to backplanes 116. Backplane controllers 114associated with backplanes 116 may calculate a skew for the timecommand. The skew may be based on the location of backplanes 116 (e.g.,the bay number) and the delay for the time command. Once the appropriateskew is calculated, backplane controllers 114 may adjust the time domainof associated backplanes 116 based on the skewed time command in orderto synchronize two or more of backplanes 116 in one time domain.

Method 200 begins at step 202 when controller 110 may initiate a timecommand sequence to synchronize the time domains of backplanes 116. Inone embodiment, controller 110 may synchronize backplanes 116 in apredetermined order. For example, the predetermined order may besequential based on the bay number housing backplanes 116. In anotherexample, the predetermined order may be based on the organization of thedevices associated with backplanes 116 into logical groups. In anotherembodiment, controller 110 may synchronize backplanes 116 on an asneeded basis. For example, a device may be hot plugged into informationhandling system 100 during operation or a device associated withbackplanes 116 may wake up after a time period in a sleep or inactivemode such that the time domain for the device is asynchronous from thetime domain of backplanes 116. In one embodiment, controller 110 mayinitiate the time command sequence by initiating a beacon routine via anI2C bus.

At step 204, controller 110 may generate a MUX control command andcommunicate the MUX control command to MUX 112 in order to select whichof backplane 116 will receive the time command. In one embodiment, theorder in which controller 110 sends the MUX control command to MUX 112may be sequential based on the bay number (e.g., a first time command issent to backplane 116A in Bay 0, a second time command is sent tobackplane 116B in Bay 1, etc). In other embodiments, the order in whichcontroller 110 sends the MUX control command to MUX 112 to select one ofbackplanes 116 may be predetermined based on the organization of thedevices associated with backplanes 116 into logical groups. For example,the devices associated with backplanes 116A and 116C as illustrated inFIG. 1A may be a logical group. Controller 110 may generate the MUXcontrol command to select one of backplanes 116 based on bay numberssuch that the MUX control command may be used by MUX 112 to first selectbackplane 116A in Bay 0 and subsequently select backplane 116C in Bay 2.

At step 206, controller 110 may generate a status command and send thestatus command to the selected one of backplanes 116. For example, thesynchronization order for backplanes 116 may be based on bay number andcontroller 110 may send the first broadcast of the status command tobackplane 116A in Bay 0. At step 208, the status command may be used todetermine the state of backplane 116A, e.g., whether a device isassociated with backplane 116A and whether that device is active. If thestatus command determines that a device is not present and/or the deviceis not active, controller 110 may enter a wait state at step 210 andreturn to step 202 to initiate another time command sequence for thenext bay (e.g., Bay 1).

If the status command determines that a device associated with backplane116A is present and active, controller 110 may send a time command at apredetermined interval to backplane 116A at step 212. In one embodiment,backplane controller 114A associated with backplane 116A may generate aninterrupt when the time command is received. Once the time command isreceived, backplane controller 114A may calculate a skew for the timecommand at step 214. The calculated skew may be based at least on theassociated bay information (e.g., the bay number) and the duration ofthe time command. In some embodiments, the duration of the time commandmay include the time at which the time command was generated, the timefor generating the time command and the delay in communicating the timecommand from controller 110 to backplane 116A. Once backplane controller114A calculates the skew for the time command, backplane controller 114Amay adjust the time domain of backplane 116A based on the skewed timecommand at step 216 in order to synchronize the time domain of backplane116A.

At step 218, controller 110 determines whether backplanes 116 ininformation handling system 100 have been synchronized. If not allbackplanes 116 have been synchronized, controller 110 returns to step202 to synchronize the next one of backplanes 116 in the predeterminedorder. If all backplanes 116 have been synchronized, method 200 ends. Inone embodiment, each of backplanes 116A-n may be synchronized to be inthe same time domain. In other embodiments, backplanes 116 may bedivided into one or more groups such that the backplanes in the groupmay be synchronized to be in one time domain.

While the above examples illustrate a system and method for providing atime command to substantially synchronize the time in each of backplanes116, the system and method of the present disclosure may be used toprovide a time command for other applications. In some embodiments, eachof backplanes 116 may include visual indicator 120 (as illustrated inFIGS. 1A and 1B), such as, for example, an alpha-numeric display, alight emitting diode (LED), etc. Visual indicator 120 may provide avisual status of each backplane 116 to administrators, serviceindividuals, and/or other users of backplanes 116. For example, visualindicators 120 may be used to determine if backplanes 116 havesynchronized time domains. In one embodiment, each of backplanes 116 mayinclude a LED indicator. If backplanes 116 are synchronized, theassociated LED indicators of each backplane 116 may substantially“blink” at the same time. If any one of backplanes 116 are out of synctime-wise, the associated LED indicator may blink at a different rate.In some embodiments, the status of backplanes 116 may be communicatedback to controller 110 in the form of data from a read of statusregister or some other method.

In some embodiments, controller 110 may be configured to provide a timecommand that allows for grouping two or more devices associated withbackplanes 116 based on, for example, domain information, topographyinformation (e.g., size, speed, type of storage resource, and/or othercharacteristics of backplanes 116), technology controller, RAIDconfiguration, and/or the utilization of two or more backplanes.Backplane controllers 114 may calculate a skew for the time command suchthat the visual indicators 120 of the grouped backplanes 116 are insync, e.g., LED indicators blink at substantially the same time,allowing for easy, visual confirmation by a user.

The examples illustrated above have the advantages of utilizing existinginfrastructures to synchronize backplanes 116 in information handlingsystem 100 without the requirement of extra hardware. Additionally, thepresent disclosure provides a system and method for synchronizingdevices associated with backplanes 116 located in different bays basedon the location of a bay.

Although the present disclosure has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereto without departing from the spirit and the scope of thedisclosure as defined by the appended claims.

What is claimed is:
 1. An information handling system configured toprovide time synchronization in a backplane, the information handlingsystem comprising: a controller configured to generate a time command ata predetermined time interval; a multiplexer communicatively coupled tothe controller; and a backplane communicatively coupled to thecontroller, the backplane including a backplane controller configuredto: receive the time command from the controller; calculate a skew forthe time command based at least on a location of the backplane and adelay caused by a multiplexer, the multiplexer communicatively coupledbetween the backplane and the controller; and adjust a time domain forthe backplane based on the skew for the time command.
 2. The informationhandling system of claim 1, wherein the controller comprises a baseboardmanagement controller or a random access card controller.
 3. Theinformation handling system of claim 1, wherein the backplane controllercomprises a storage enclosure processor controller.
 4. The informationhandling system of claim 1, wherein the backplane controller is furtherconfigured to calculate the skew for the time command based at least onone of a setup delay, a toggle delay, and synchronization delay.
 5. Theinformation handling system of claim 1, further comprising: thebackplane controller configured to: receive the time command from thecontroller at a first time; calculate the skew for the time commandbased at least on the location of the backplane and the first time; andadjust the time domain for the backplane based on the skew for the timecommand; and a second backplane communicatively coupled to thecontroller, the second backplane including a second backplane controllerconfigured to: receive the time command from the controller at a secondtime; calculate a second skew for the time command based at least on alocation of the second backplane and the second time; and adjust asecond time domain for the second backplane based on the second skew forthe time command such that the time domain and the second time domainare synchronized.
 6. The information handling system of claim 1, furthercomprising a plurality of backplanes organized in at least one logicalgroup.
 7. The information handling system of claim 1, furthercomprising: a second backplane communicatively coupled to the backplane.8. The information handling system of claim 7, wherein the backplanecontroller is configured to: determine a delay time based at least onthe delay time caused by the backplane; and provide a new time commandto the second backplane based at least on the delay time caused by thebackplane.
 9. A backplane comprising a controller including: aprocessor; a memory communicatively coupled to the processor; andprocessing instructions encoded in the memory, the processinginstructions, when executed by the processor, operable to performoperations comprising: receiving a time command; calculating a skew forthe time command based at least on a location of the backplane and atransmittal delay caused by a multiplexer communicatively coupledbetween the backplane and the controller; and adjusting a time domainfor the backplane based on the calculated skew for the time command tosynchronize the backplane.
 10. The controller of claim 9, wherein theprocessing instructions are further operable to perform operationscomprising calculating the skew for the time command based at least on abroadcast time for the time command.
 11. The controller of claim 9,wherein the processing instructions are further operable to performoperations comprising calculating the skew for the time command based atleast on one of a setup delay, a toggle delay, and synchronizationdelay.
 12. The controller of claim 9, wherein the controller comprises astorage enclosure processor controller.
 13. A method for providing timesynchronization in a backplane, the method comprising: receiving a timecommand from a controller at a backplane controller, the backplanecontroller associated with a backplane; calculating a skew for the timecommand based at least on a location of the backplane and a transmittaldelay caused by a multiplexer communicatively coupled between thecontroller and the backplane; and adjusting a time domain for thebackplane based on the calculated skew for the time command tosynchronize the backplane.
 14. The method of claim 13, wherein thecontroller comprises a baseboard management controller or a randomaccess card controller.
 15. The method of claim 13, wherein thebackplane controller comprises a storage enclosure processor controller.16. The method of claim 13, wherein calculating the skew for the timecommand further comprises calculating the skew based at least on abroadcast time for the time command.
 17. The method of claim 13,calculating the skew for the time command further comprises calculatingthe skew based at least on one of a setup delay, a toggle delay, andsynchronization delay.